1 /* 2 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_RUNTIME_TASK_HPP 26 #define SHARE_RUNTIME_TASK_HPP 27 28 #include "memory/allocation.hpp" 29 #include "runtime/timer.hpp" 30 31 // A PeriodicTask has the sole purpose of executing its task 32 // function with regular intervals. 33 // Usage: 34 // PeriodicTask pf(10); 35 // pf.enroll(); 36 // ... 37 // pf.disenroll(); 38 39 class PeriodicTask: public CHeapObj<mtInternal> { 40 public: 41 // Useful constants. 42 // The interval constants are used to ensure the declared interval 43 // is appropriate; it must be between min_interval and max_interval, 44 // and have a granularity of interval_gran (all in millis). 45 enum { max_tasks = 10, // Max number of periodic tasks in system 46 interval_gran = 10, 47 min_interval = 10, 48 max_interval = 10000 }; 49 num_tasks()50 static int num_tasks() { return _num_tasks; } 51 52 private: 53 int _counter; 54 const int _interval; 55 56 static int _num_tasks; 57 static PeriodicTask* _tasks[PeriodicTask::max_tasks]; 58 // Can only be called by the WatcherThread 59 static void real_time_tick(int delay_time); 60 61 // Only the WatcherThread can cause us to execute PeriodicTasks 62 friend class WatcherThread; 63 public: 64 PeriodicTask(size_t interval_time); // interval is in milliseconds of elapsed time 65 ~PeriodicTask(); 66 67 // Make the task active 68 // For dynamic enrollment at the time T, the task will execute somewhere 69 // between T and T + interval_time. 70 void enroll(); 71 72 // Make the task deactive 73 void disenroll(); 74 execute_if_pending(int delay_time)75 void execute_if_pending(int delay_time) { 76 // make sure we don't overflow 77 jlong tmp = (jlong) _counter + (jlong) delay_time; 78 79 if (tmp >= (jlong) _interval) { 80 _counter = 0; 81 task(); 82 } else { 83 _counter += delay_time; 84 } 85 } 86 87 // Returns how long (time in milliseconds) before the next time we should 88 // execute this task. time_to_next_interval() const89 int time_to_next_interval() const { 90 assert(_interval > _counter, "task counter greater than interval?"); 91 return _interval - _counter; 92 } 93 94 // Calculate when the next periodic task will fire. 95 // Called by the WatcherThread's run method. 96 // Requires the PeriodicTask_lock. 97 static int time_to_wait(); 98 99 // The task to perform at each period 100 virtual void task() = 0; 101 }; 102 103 #endif // SHARE_RUNTIME_TASK_HPP 104